CVE-2025-20324: Splunk Enterprise Auth Bypass Vulnerability

CVE-2025-20324 Overview

CVE-2025-20324 is an Improper Access Control vulnerability affecting Splunk Enterprise and Splunk Cloud Platform. A low-privileged user that does not hold the "admin" or "power" Splunk roles could create or overwrite system source type configurations by sending a specially-crafted payload to the /servicesNS/nobody/search/admin/sourcetypes/ REST endpoint on the Splunk management port. This vulnerability allows unauthorized modification of critical system configurations, potentially impacting data ingestion and security monitoring integrity.

Critical Impact

Low-privileged users can bypass authorization controls to create or overwrite system source type configurations, potentially disrupting data parsing, log ingestion, and security monitoring capabilities across the Splunk deployment.

Affected Products

• Splunk Enterprise versions below 9.4.2, 9.3.5, 9.2.7, and 9.1.10
• Splunk Cloud Platform versions below 9.3.2411.104, 9.3.2408.113, and 9.2.2406.119

Discovery Timeline

• July 7, 2025 - CVE-2025-20324 published to NVD
• July 21, 2025 - Last updated in NVD database

Technical Details for CVE-2025-20324

Vulnerability Analysis

This vulnerability is classified under CWE-284 (Improper Access Control), indicating a failure in the authorization mechanism that should restrict access to sensitive administrative functions. The flaw exists in the Splunk REST API endpoint responsible for managing source type configurations.

Source types in Splunk are fundamental components that define how incoming data is parsed, indexed, and categorized. They control critical aspects of data processing including timestamp extraction, line breaking, and field extraction. System source types are typically reserved for administrative users due to their impact on the entire Splunk deployment.

The vulnerability allows users with minimal privileges to bypass the intended role-based access controls and directly manipulate these critical configurations through the management port REST API.

Root Cause

The root cause is an authorization bypass in the /servicesNS/nobody/search/admin/sourcetypes/ REST endpoint. The endpoint fails to properly validate that the requesting user possesses the required "admin" or "power" Splunk roles before processing requests to create or modify system source type configurations. This allows authenticated users with lower privilege levels to perform administrative actions that should be restricted.

Attack Vector

The attack is network-based and requires the attacker to have valid authentication credentials for the Splunk instance, even at a low-privilege level. The attacker sends specially-crafted HTTP requests to the vulnerable REST endpoint on the Splunk management port (default TCP port 8089).

An attacker could leverage this vulnerability to:

• Overwrite existing system source types to alter how specific data is parsed
• Create malicious source type configurations to evade detection
• Disrupt data ingestion by corrupting source type definitions
• Potentially hide malicious activity by modifying how security logs are processed

The attack does not require user interaction and can be executed remotely against any accessible Splunk management interface.

Detection Methods for CVE-2025-20324

Indicators of Compromise

• Unexpected modifications to system source type configurations in $SPLUNK_HOME/etc/system/local/props.conf
• Audit logs showing source type API calls from non-admin users to the /servicesNS/nobody/search/admin/sourcetypes/ endpoint
• New or modified source types that were not created through normal administrative processes
• Changes to source type configurations that impact data parsing or timestamp recognition

Detection Strategies

• Monitor Splunk's internal audit logs for REST API calls to the sourcetypes endpoint from users without admin or power roles
• Implement file integrity monitoring on Splunk configuration files, particularly props.conf and transforms.conf
• Create alerts for unauthorized modifications to system-level source type configurations
• Review access patterns to the Splunk management port (TCP 8089) for anomalous activity

Monitoring Recommendations

• Enable verbose audit logging for REST API calls on the Splunk management port
• Establish baseline configurations for source types and alert on deviations
• Monitor for privilege escalation attempts or unauthorized administrative actions in Splunk audit logs
• Implement network segmentation to restrict access to the Splunk management port to authorized administrative networks only

How to Mitigate CVE-2025-20324

Immediate Actions Required

• Upgrade Splunk Enterprise to versions 9.4.2, 9.3.5, 9.2.7, or 9.1.10 or later depending on your version track
• Upgrade Splunk Cloud Platform to versions 9.3.2411.104, 9.3.2408.113, or 9.2.2406.119 or later
• Restrict network access to the Splunk management port (TCP 8089) to authorized administrative hosts only
• Audit current source type configurations for any unauthorized modifications
• Review user accounts and ensure principle of least privilege is applied

Patch Information

Splunk has released security patches addressing this vulnerability. Detailed information is available in the Splunk Security Advisory SVD-2025-0707. Organizations should prioritize upgrading to the fixed versions as outlined in the advisory.

For Splunk Enterprise, the following versions contain the fix:

• Version 9.4.2 and later for the 9.4.x branch
• Version 9.3.5 and later for the 9.3.x branch
• Version 9.2.7 and later for the 9.2.x branch
• Version 9.1.10 and later for the 9.1.x branch

Workarounds

• Implement firewall rules to restrict access to the Splunk management port (TCP 8089) to trusted administrative networks only
• Review and minimize the number of user accounts with access to the Splunk instance
• Enable enhanced audit logging to detect any exploitation attempts while awaiting patch deployment
• Consider implementing a web application firewall (WAF) to filter malicious requests to the management API

# Example: Restrict management port access using iptables
# Allow only specific admin network to access Splunk management port
iptables -A INPUT -p tcp --dport 8089 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8089 -j DROP